Nobody goes to a Britney Spears concert to be blown away by the dulcet quality of her live vocals — but even so, it doesn’t seem unreasonable to expect the pop superstar to mouth along to her own backing track.

And yet, viewers who flocked to Spears’ Las Vegas residency Piece of Meon Tuesday night were treated to a rare flub from the consummate performer, as she failed to sing into the microphone during a rendition of her Britney Jean song “Alien” — and the vocal track kept right on playing. Fortunately, all her fans know that she isn’t singing live in the first place, so it’s not exactly disillusioning — and in fairness, she was probably just too busy being iconic to be bothered.